Consequences of Failed Interlock – When the Grid Feeds Your (out-of-sync) Generator


New member
Nova Scotia, Canada
First things first: this did not happen to me.

Second - Long story short: I’m doing some research into cyber warfare as part of an academic project, and I came across something that I think will be of interest to the Steel Soldiers crew: the Aurora Generator Test.

Quick Summary: In 2007, while investigating the cyber vulnerabilities of the national power grid, a test was conducted (by the Department of Homeland Security) where a 2.25MW diesel generator was used to supply power to a fake/test electrical grid. The generator was synchronized to the grid and connected via a computer-controlled relay which, if the generator was out of sync with the grid, would not allow it the relay to close. The relay’s code was modified (simulated cyber attack) to deliberately cause the relay to open when the generator was in sync with the grid, and close when out of sync, effectively causing the generator to instantly, and violently, synchronize with the utility grid. This opening and closing was repeated four times in a few minutes, which caused a catastrophic failure of the gen set (prime mover and alternator).


So, for those who wonder what could happen if their beloved MEP was connected to their home without an interlock/isolation from the grid when the power was restored (saying nothing of the risk to utility workers while you backfeed the grid), watch this:

Test Footage:

Stay safe!



Well-known member
Steel Soldiers Supporter
West greenwich/RI
Oh yea... not a good thing to mis-match the syncronization! The lesser of the sources will instantaneously " correct itself" violently and in this case catastrophically! I was actually expecting a much louder bang when the relay closed, but still amazing to see the gen jump up in the air.


Well-known member
Definitely a thing to watch. We had one at a water plant (wasnt syncing utility was 2 paralleled sets) and the operator misread the syncroscope. Tldr one gen set jumped off its pad.

Sent from my SM-G973U using Tapatalk


Well-known member
Steel Soldiers Supporter
Our REMC electric company would drop out, causing CNC and computers to crash and then come back on, often out of phase. You can't imagine the damage that does. The company wanted to consolidate another company but refused to bring it to Indiana because of the utility. We lost 70 jobs because the utility was saving money when it switched from one supplier to another to save $$$... not even paying attention to what their customers had to deal with because of their negligence aligning phases. The entire issue got ugly because the utility management denied what they were doing. I was about to chart record but the company gave up and had me move the other manufacturer to Ohio....then closed this location, another 50 jobs lost.

Light in the Dark

Well-known member
Steel Soldiers Supporter
That is no marshmallow taking a tumble off a picnic table... I actually thought it would have failed in a more spectacular fashion... but all the same, glad I was nowhere near that.


Resident railroad expert
Steel Soldiers Supporter
Hopkins, SC
Reminds me of the time I accidentally used the parallel two ships generators together procedure, to bring us off the pier and onto ships power to get underway.

For a split second our 2,000kw gas turbine generator tried to match power output with the Norfolk city power grid... if I hadn't had my finger already hovering over the shore power breaker and if it hadn't opened when I hit it, I'd probably still be making small rocks out of big ones by hand in Leavenworth to pay for it. All the lights did crazy stuff, motors made horrible sounds, all the gauges buried themselves... Chief engineer had already come aboard and as soon as the shore breaker opened and everything normalized the phone on the desk rang with him going $&*@*$^!% was that!!!!!

I got very lucky that day...


Well-known member
Burgkunstadt, Germany
The surge from out of sync connection will cause blown fuse or breaker to trip.
I saw this happen in front of my eyes in 1973, at Ft. Belvoir, Va. At the time it was the Power Generation School for the Army. Every relay, every set of contact, every switch and on and on, had to be replaced. We were all a little flash blinded. The controls were behind plexiglass, to allow us students to see what happens when the Parallel operation went right. A stupid student showed us what happens when you close the output CB, on the gen set and the Parallel lights were on. OH BABY.

I also saw a gen set "hop" like the one in the clip. It was a 60 KW gen set from a ROWPU Water Purification Unit. The owning unit replaced the main gen. The schematics show how to thread the main gen output wires through the Power Transformers, for both the 30 KW and 60 KW. The unit wrapped the wires through the Power Transformer in the 30 KW configuration. So the transformers were seeing twice the real load. Then the unit kept getting overload failures. So they loaded the get set with a 60 KW load, and dropped the full 60 KW load on the set at once. The gen set was sensing a "120" KW load. Of course it shut the CB off. But in the instance that the CB was closed. The set "hopped" high enough to come off the floor. Just like the video showed, parts went flying in every direction. Most disturbing.

That was a great film clip!
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